Hydrophone



June 8 1926. 1,587,890 w. H. BARBER HYDROPHONE Filed May 25. 1921 3 Sheets-Sheet 1 Jun 8 1926;

W. H. BARBER HYDROPHONE Filed May 25, 1921 .'5 Sheets-Sheet 2 xmmmmmwmmwt June 8 1926. 1,587,890

' W, H.'BARBER HYDROPHONE Filed May 25, 1921 4 3 sheets-sheet 5 Patented .lune Si,

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WALTER H. BARBER, 0F STONEHAldl-. MASSACHUSETTS, ASSIGNOB T0 SUBMARIN'E SIGNAL COMPANY, QF ORTLAND, IIIAENE, CORE'ORATION OF MAINE.

HYDROPHONE.

Application 'Filed May 25,

I have made a new and useful improvement in apparatus suitable .for detecting` under-water sounds. Heretotore microphones have been used as a portion of submarine signaling apparatus to detect the sounds which are created when bells are struck under water or when a series of undaniped sound waves produced under water by such a device as an oscillator. Such microphones were. in ejeneral1 designed to be most responsive to notes ot the frequency ot the signalingy source and efforts were made to arrange the microphone and its mounting in such a way that it was responsive only to sounds ot the frequency ot the signaling source.

rlhe microphone or hydrophone which l have invented has tor its object, not merely the detection ot a sound ot definite or sustained pitch, but also the detection ot all sounds` so that vthe hydrophone will give .immediate indication ot ships, whether visible or invisible, or other moving vessel such as a submarine as well as of musical or bell noises. As there may be more than one vessel creating submarine noises within the range ot the hydrophone, .it is of 'fundamental importance that a hydrophone to have the greatest usefulness should reproduce the characteristics ot the sounds created by each source ot sound waves. ln other words, the hydrophone a whole must be as nearly as possible tree 'from any characteristics ot its own, or must he what may be called aperiodic. As these hydrophones will be used in most cases with compensators tor the ascertainment ot the direction and position ot the invisible sound source, the two or three hydrophones used in conjunction .tor this purpose must be similar in volume and have as nearly as nay be possible the same characteristics,

My invention consists ot a new form ot ciu'rent-varying element, or as it will be called microphone button or button for use in hydrophones designed especially for uses as submarine sound detectors and with direction-finding; devices.

button tor a hydrophone used to detrot ships noises must be equally sensitive at all times even to sounds ot the smallest intensity; and must be so made as to have the least possible natural pitch oit its own. lhe first of these requirements l have obtained by so designing` the carbon chamber 1921. Serial N0. 472,538.

and by using such amounts of carbon as will allow just the right ar-mount ot current to pass at all times and will never admit a rise in current strength sutiicient to overheat the button and thus produce packing, that is, a short-circuiting ot the button through something, analogous to the coherer action which is well known in detectors for wireless signals. l have accomplished this by using` a washer et highly elastic insulatingry material. rll`his Washer is held between the two electrodes which form `the front and back of 'thel carbon chamber. Holes are made through this washer of a size and shape such that the necessary amount of carbon will be contained in the pockets thus formed, and the washer` is soplaced in the button and the button is so mounted in the hydrophone case that there is never too great a pressure, arising `trom gravity, of the carbon within a pocket. It is known that telt or velour washers have been used in microphones and that holes have been punch ed in these washers to form chambers tor the reception of the granular carbon, but the form and size of these chambers have tailed to give the extraordinary results, both in uniformity and sensitiveness, which l have obtained in button when used as a noisc-detecting` hydrophone.

l have likewise obtained unusual sensitiveness in my button by the shape which has been given to the front electrode. As stated above, it is ot' fundamental importance to have the button ot the requisite resistance and this can be obtained only by having` a fairly large electrode surface as well as a proper amount ot granular carbon between the electrode surfaces. It is also important to keep the weight ot the button as light as may be reasonably possible and, as a consequence, the size ot the complete button must be kept small. The sensitiveness ot the button can be increased by increasing; the tree or unclamped area of the elastic disk or washer, which supports the front electrode, and by means of which the front electrode is held mechanically uponthe case oit the button. `I have obtained this necessary sensitiveness preferably by undercutting or chamiiering the piece to which the iront electrode is attached so as to retain a lull-sized iront electrode and, at the same time.I obtain a greater freedom of the elastic member which supports the button than has hitherto `been found possible with the small sized button which I employ.

Still another feature of my button Which has been .discovered after years of trial (the physical signilicance `of which I have been unable to explain satisfactorily) is the use of tivo elastic members similar in all respects, clamped togetherso as to operate virtually as a single elastic member. Hitherto the elastic ymember has been a ,single .disk .or plate of mica or other elastic material, .or tivo yorrnore elastic disks kseparated from .each other. I have found that by the use of .tivo `elastic members clamped together, y as if they were .a single member, I can obtain a more .characteristic Voriginal source of .sound with rgreater freedom from individual characteristic tones und at the sarne time lwith increased rather than `decreased sensitiveness to feeble sounds from the source. f

My invention will .be understood by reference to .the draw-ing in which it is .shown .in its preferred form.

Figure l ,shows a `side .elevation of the hydrophone, the vieu7 being partly in section .to show the mounting of the button.

Fig. 2 is a sectional view of all the parts `of the button except the frame which is in eleva-tion, the parts being shown in .unassembled relation.

Fig. 3 is a plan .of the elastic Washer, and

Fig. el is a section showing vthe assembly 0f the parts.

Fig. 5 shows in vertical section a form fof mounting useful Where the hydrophone :used in a tank on boa-rd ship..

Fig. ,6 is a side l,elevation thereof.

Fig. 7 is a front View of a. -support by which the hydrophone may Ibe arranged to hang in substantially horizontal position.

Fig. :8 shows .the same support in Iclosed or gripping position.

` Fig. `9 is a section on line 9 9 of Fig. 7, land Fig. 10 is .a reduced fragmentary :section fof the tank With the hydrophone supported therein.

l .is a metal containing case or cup in the bottom of Awhich issofldered by solder 100 the bacl electrode 2. I have used highly polished carbon for the acti-ve face of this back electrode, but :a highly polished Vsurface of metal which does not oxidize may equally Well be employed. A Washer 3 of fel-t or any other elastic nonacondueting material is inserted in the cup and iills with `the least possible .compression the space between the hack electrode 2 Aand front :electrode 6. The Washer 3 i-s shown .-a-s having slots 4 .and 5 which when the Washer is in place between 2 and 6 form tivo cavi-ties in which the granular .carbon placed. A plan view .ofwasher 3 is shown in Fig. 8. An important feature of this Washer is the general shape of the reproduction of the.

.screw tnread 9 of brass piece cavities or chambers which provides for a considerable bulk of carbon which may be extended laterally across the greater portion of the diameter of .the Washer in comparatively thi-n layers so that ythe packing effect ofgravity is negligible, and at the same time sufficient granular carbon may be used to securegood results. When assembled in the button the Washer 3 is so placed that the slots .have their greatest dimensions horizontally. The active f-ront surface of electrode 6 may be made as large possible so as to cover slots l and 5 .in Washer 3 and thus prevent ythe granular carbon from falling or Working its Way out from the cavities. This front electrode 6 has va highly polished sur face Where it bears upon the granular .carbon. Electrode 6 has been made of carbon in the .buttons lWhich I have mani-ifactured, but any conducto-r which can be highly poli-shed and Will not corrode may be used. As shown, the front electrode .6 is soldered to metal piece 7 the front face -of which is .thinned -near its edge rto .allow the disks 10 and 13 to have considerable play near their edges, -their central clamped area thus being considerably less than .the active area of the elect-rode f6.

Piece 7 Ahas a smooth shank at S for a distance .a little less than the :thiclmess of clamping washer 14, and has the remainder of .the shank threaded at 9. l0 and lf3 are two similar disks of elastic insulating inaterial formi-ng together a. laminated ldiaphragm. I have found mica ive/ll suited for the purpose. Holes Il and l2 in .disks 10 and 13, respectively, permit these disks to passed overshank 8. The clamping Washer 14 Ihas the same outside diameter as the thicker part of the piece 7 and has a hole l5 through i-t of -a diameter such :that it can just pass onto shank 8 of brass piece 7. Clamping nut 16 has a threaded hole 17 which permits it to be screwed onto the l 7. Thus when this portion .of the button is assembled the `tivo mica Washers are firmly clamped a-ttheir middle between brass piece 7 and nut 14 and at their edges by .the crimping ring 18, the points on the clamped discs 10 and 13 comprising the diaphragm bet-Ween the crimping ring 118 and the clamping nut 16, being free to move so that an unusual 4amount of vibration is ,give-n to the diaphragm by the electrode, the portion of the diaphragm which is free to move being of smaller internal diameter than the diameter of the electrode. It will be understood .that the electrode and its support may be integral if desired. I have adopted this mechanical construction and used clamping nut 16, rather .than threading Washer lat, and using it for the clamping nut, tor the reason that I have found by very careful experiment that, if Washer la*- is turned against the surface of disk l?) during the assembly ot the button, as would have to be done ii were threaded and used as a clamping;` nut) the surface ot the. elastic disk i3 would be out or scratched suliiciently to seriously atleettlie operatiiug` eilieiency ol. the button. 1S is the crimping ring' which is passed over the cup 1. lVhen the entire button above described has been assembled with the requisite .carbon in pockets 4l and it is placed in a` press and the crimping ring 18 is Yforced upon the cup l under great pressure by means ot a device well known. rl`he liange 19 of the crimping' ring is turned about the flange 20 oic the cup, thus tirmly binding the elastic disks l0 and l?, between the crimping ring` and the top surface of the rim 2O ot cup l and thus retaining the elastic disks* firmly bound between the crimping ring and the cup and consequently holding' all other portions of the button in their proper positions. Thus the vibrator'v areay et the but ton is large in proportion to the diameter of the button and is capable ot' greater treedom and amplitude ot vibration than is usual in other buttons of the same sis'.

In order to make connection with the button without in any way restrictingthe freedom ot' movenient otl the button, l preter to use a light metal rectangular trame 2l. This trame .is larpge enough to surround 'the button and has a. hole 22 through one side to receive the end oit screw 9 which passes throiuih it and is held by nut 26. At the opposite side are two pins Q3 and :511i one ot which 23 insulated trom the trame by suitable bushings The trame and pin thus 'Form the connection with the 'liront electrode and flexible wire soldered to cup l and to piu 723 terms the connection with the back electrode.

Fia'. l. shows a button such as has been described above mounted in a. forni ot hydrophone made in two parts 27, 28, which has been extensively used in the detection otl noises produred by distant ships. The case et this hydrophone is reasonably aperiodic, being; made. ot rubber and in two parts QT, titl. lllithiu is a sleeve Q9 grooved as at 3() to receive the outer rubber casing which lills these grooves, the sleeve thus holding these parte 'l'.ogiether. lllithin this sleeve is f core Pil which acts as a stelling box and carries the conneeting` wires and terminals SZ to which the leaf; troni pins and Qd are connected. The trame 2l is attached to the interior oli the casing member 27 by the serew which screws into a socket in a metal piece SiS-3 moulded in the casing member 27. Z4- is a damping' ring to clamp the rubber .iglitly against the sleeve 29. lt may be used to haue' the hydrophone to a suitable float.

ln the torni ot my invention shown in Fig. 5 the button is supported in a rubber casing one portion olf whicli is marked 27.

The part 2T carries a metal piece to which the button is attache-d by the ew 9 as betere. A llangied metal sleeve 'forms the side walls ot the chamber within the hydrophone aud around this sleeve lies a sleeve 36 projecting' trom the other member Si' ot the hydrophone casing, which carries preise ably a lead disk 39 torming one ot the ends ot the chai'nber.

The leads from the terminals E52 are enclosed in a cable Ll0 which passes up through a tube --jl. forming part of the member 37 and profe ibly the cable is cemented to the interior or the tube or otherwise attached thereto to pil-event leakage. Around the hydrophone approximately midway between .its two en is a strap 3411 having` a piece l2 which projects upwardly and carries a yoke 4?). The strap 341 is open at one side and provided with a hook member 342 adapted tocatch over the shoulder on the other end oi? the strap so that, shown in Fig. 8, where the strap is placed about the hydrophone, tliefctwf.) ends ot the strap will overlap and the hook catch onto the shoulder and the two may then be fastened by the screw 344i, as shown in Fig. 6. rl'he tube 4.1 then passed up into the yoke et?) and the ends of the yoke are bent around as shown in dotted lines in Fig. 9 so that 'when suspended by the tube l-l the hydrophone will hang substantially in a horizontal position, this position being assisted by the weight ot the disk 39 which balances the weight ot the flange of sleeve 35.

ln Fig. l0, lfl indicates a tank on board ship which is filled with water and in which the hydrophone is submerged. The tube 4.5i sutliciently longto pass out through the top of the tank 4A, a stuiliiug` bott. being used it desired so that the water is never in contact with the leads.

l have described above an instrument which has shown itself to be an improvement over microphones heretofore used as sound receivers in the submarine art and so i'ar as I know it is the best embodiment ot my invention now known to me, but l do not mean to limit myself to the precise construction shown. Its practical advantages seem to result from the use ot a laminated member or diaphragm to piek up the sound waves (this laminated. member being substantially aperiodie) and the means described 'for containing the carbon granules whereby there is secured a minimum tend ency tor the granules to pac-k. This device has been thorougijhly tested and has proved itselt particularly eflicient in use.

llhat l claim as my invention is l. A microphone button comprising two electrodes and a diaphragm comprising separate and independent disks ot elastic material ot' the same diameter in contact and clamped together at their edges to form a Single vhratable member, said disks having the same eoeeent of expansion, one of said electrodes being connected to said Acha- .phrngxn to more therewith.

2. A microphone button Comprising an electrode support having zur electrode attached thereto, said support havin-g an edge thnner'than its central portion, and a da phragln clamped to and in `Contact with Enid central portion only and exten-ding beyond the thinner edge of said support whereby its vibrations will not be damped thereby.

VALTER H. BARBER. 

